1. Field of the Invention
The present application pertains to tire construction. Specifically, it pertains to construction of an improved radial tire. Even more specifically, it pertains to improved off-road, high flotation, low pressure tires of radial construction.
2. Brief Description of the Prior Art
Radial tires have been well accepted for many years for highway use on most vehicles. In addition, some radial tires have also been used for low speed, off-road vehicles, such as swamp buggies, logging vehicles, agricultural vehicles and the like. For swamp and logging vehicles, one type of tire frequently used is a high flotation, low pressure tire in which the width of the tire may be equal to or greater than its diameter. Such tires are typically mechanically clamped to a hub or wheel by means of a keeper ring so that they do not rely on internal air pressure to keep the tire bead seated on the hub or wheel. The recommended tire pressure for such a tire typically does not exceed fifteen psi and the speed of the vehicles on which they are used do not usually exceed twenty mph.
The carcass of a high flotation, low pressure tire of radial construction may be formed of a plurality of plies of radial cord extending from one of the tire beads, radially along an associated sidewall, along its cylindrical mid-section and radially along the other sidewall to the other tire bead and a plurality of plies of circumferentially disposed tire cord surrounding the substantially cylindrical mid-section. The radial plies are typically applied in strips of parallel (side-by-side) tire cords encapsulated or calendered in rubber. As indicated, the tire cords are parallel and adjacent to each other with typically eighteen to twenty two cords per inch of width. Generally no woven tire cord is used in the industry because with such construction the cords tend to cut on each other during flexure and may also result in minute voids in the rubber where cords cross and contact each other. Both of these conditions could contribute to tire failure.
At least one off-road tire of the high flotation, low pressure radial construction type is shown in U.S. Pat. No. 4,589,460. While such tires function well from a support, stability, flexibility and general wear standpoint, they are not without some problems. Because of the way the radial plies are applied and due to the great amount of flexure thereof, the sidewalls of such a tire are, under severe service conditions, somewhat susceptible to punctures, fractures, radial rips and the like due to rocks, stumps and other obstacles with which these sidewalls may come in contact. Thus, it is possible that an expensive high flotation, low pressure radial tire may become useless even though, from a general wear standpoint, it may have many hours of service life left therein.